Water-soluble acid esters of polyoxyalkylenated pentaerythritol in silver halide emulsions



United States Patent 3,532,501 WATER-SOLUBLE ACID ESTERS OF POLY- OXYALKYLENATED PENTAERYTHRITOL IN SILVER HALIDE EMULSIONS E Scudder Mackey, Arthur L. York, and Fritz Dersch, Binghamton, N.Y., assignors to GAF Corporation, a corporation of Delaware No Drawing. Filed Feb. 10, 1967, Ser. No. 615,085 Int. Cl. G03c 1/28, 1/78 US. Cl. 96-107 9 Claims ABSTRACT OF THE DISCLOSURE Sensitizing agents for photographic silver halide emulsions having anti-static properties, comprising water-soluble acid esters of polyoxyalkylenated pentaerythritol.

The present invention relates in general to the provision of novel additives for improving the sensitivity, anti-static properties, covering power, etc. of photographic silver halide emulsions and in particular to the employment of certain derivatives of pentaerythritol for such purposes.

As is well known, the sensitivity of light-sensitive silver halide emulsions can be increased in a number of ways as for example, by the incorporation therein of one or more chemical or optical sensitizing agents which function to augment and/or extend the emulsion sensitivity to light of longer wave lengths.

In general, it is postulated that chemical sensitization results from the formation of small amounts of silver sulfide and/ or silver on the surface of the silver halide crystal. As examples of compounds found to function as chemical sensitizing agents there may be mentioned sodiu-m sulfite, sodium thiosulfate, and the like.

Heretofore, a wide variety of compounds has been suggested for purposes of increasing the spectral sensitivity of photographic silver halide emulsions. Particularly bene ficial results are purportedly obtained with such compounds as the polyoxyalkylene ethers and numerous derivatives thereof such as the products obtained by reacting alkylene oxide with reactive hydrogen-containing organic compounds, i.e., acids, alcohols, amines, etc. The use of the foregoing and related compounds for such purposes, is well established in the prior art being extensively described in the patent and trade literature. In this regard reference is made to US. Pat. 2,423,549, 2,441,389, and 2,400,532, etc. In general, the polyoxyalkylenated derivatives of the type described in the aforereferenced patent literature have molecular weights in the neighborhood of at least 300 and preferably within the range of from 1500 to 10,000 or more. Other compounds proposed for use in a similar relationship include the quaternary ammonium, phosphonium and tertiary sulfonium salts as Well as combinations or mixtures of one or more of the foregoing compounds with alkylene oxide polymers.

Other problems frequently encountered in the emulsionmaking as well as the emulsion-processing industries relate to the production of relatively high speed emulsions which enable the attainment of image reproductions characterized by satisfactory contrast as well as covering power of the developed silver. As is well known, the term covering power is a measure of the silver concentration in the developed image and is derived arithmetically by dividing the optical density at maximum density by the grams of silver per square decimeter in the developed image layer.

As examples of materials heretofore promulgated for use as emulsion addenda to thereby obtain the requisite contrast, silver covering power, etc., there may be mentioned in particular the poly-N-vinyl lactams, the watersoluble polyglucose dextrans, water-soluble ,B-hydroxyice alkyl ethers of polyvinyl alcohol, water-soluble hydrolyzed glycogen, water-soluble mannan polysaccharide, the water-soluble polyglucose laminarins, hydroxy-ethyl celulose, carboxy-methylated proteins and the like.

While the foregoing and related compounds have been found in the vast majority of instances to provide some measure of improvement their use is invariably accompanied by other significant drawbacks Which tend to detract considerably from their desirability. For example, many of the foregoing compounds must of necessity be employed in inordinately large proportions resulting in a depression of the melting point of the emulsion layer which, in turn, leads to such undesirable defects as reticulation, the later becoming particularly manifest in those instances wherein theemulsion is subjected to high temperature, rapid processing. Moreover, such compound can present serious problems of fog and especially when the emulsion containing same is stored for any significant period of time under even moderately severe conditions of temperature and/or humidity. In order to eifectively counteract the fogging tendency imparted to photographic emulsions containing sensitizers of the aforedescribed type, while simultaneously making possible maximum realization of the advantageous sensitizing characteristics of such compounds, it has been necessary to utilize such sensitizers in combination with antifoggant compounds. The ineffectiveness of the more conventional antifoggant agents, such as those referred to on page 459 et seq. of Mees The Theory of the Photographic Process, published by the Macmillan Co., New York, N.Y., 1946, to suppress such fogging tendency has made imperative the use of rather costly antifoggant agents for such purposes. Representative of the latter materials are those described for example in US. Pat. 2,704,716, i.e., hydromelonic acid or cyameluric acid; US. Pat. 2,716,062, i.e., 4-hydroxy-6-alkyl-1,3,3a-7- tetrazaindenes and in US. Pat. 2,728,666, i.e., specific compounds of mercury with amines or amine salts. A further deterrent to the use of the compounds thus far known resides in their pronounced tendency to cause tur bidity either in the wet or dry state of the emulsion layer.

In an eifort to overcome or otherwise alleviate the foregoing and related disadvantages, considerable industrial research and development has centered around the provision of compounds which, when incorporated into light-sensitive silver halide emulsion layers, impart thereto acceptable photographic speed, contrast and covering power while reducing substantially any tendency of the silver halide emulsion to fog. However, desipte the extensive industrial effort in this regard, the compounds thus far suggested have been found characteristically to provide a satisfactory measure of improvement only at the expense of other essential emulsion properties.

Concomitant with the provision of silver halide emulsions possessed of high photographic speed has been a corresponding intensification of other problems which de tract considerably from the photographic quality obtainable in the final image. Particularly problematical has been the attainment of a photographic film element having the desired anti-state properties. As is generally known, in the manufacture of photographic film, a film base is coated on one or both sides with for example, a subbing composition usually comprising a dispersion of gelatin in a suitable solvent or solvent mixture so as to facilitate the adherence or anchorage of one or more of the photo-sensitive, non-curling or antihalation layers. When such a laminate is wound into a tight curl and subsequently unwound, as during the coating operation, considerable static electricity is generated and spark discharges are likely to occur. The foregoing phenomena is invariably manifested folowing development of the exposed film in the form of black streaks, lines or other irregularities which tend to create a fog pattern throughout the entire emulsion layer. In general, such spurious density deposits become more pronounced as the sensitivity and thus speed of the film material is increased. Consequently, the provision of improved sensitizing agents has made incumbent upon the film processor the inclusion in the film element of one or more substances which abate or otherwise retard the tendency of such film to accumulate such static charge or alternatively a substance which is an electrolyte or possesses hydroscopic properties in order to impart conductivity to the film and thereby expedite dissipation of such static charges before their accumulation leads to local electrical discharges.

As will be recognized, impairment of image quality becomes more pronounced, in general, as the photographic speed of the emulsion material is increased.

In US. Pat. 3,173, 790 there is described a novel class of silver halide emulsion materials which comprise alkylenated oxide adducts of pentaerythritol such polyoxalyklenated derivatives having a molecular weight ranging from about 300 to about 10,000 or more. The polyoxyalyklenated derivatives described in this patent have been ascertained to function to exceptional advantage as photographic sensitizing agents while reducing to a great extent the undesired characteristics invariably attending the use of the more conventional sensitizers. Thus, such sensitizing agents have proofed in practice to provide efficacious sensitizing results when incorporated into silver halide emulsions while being substantially devoid of the excessive fogging previously encountered. Moreover, any fogging problems which might arise in connection with the use of such sensitizing agents can usually be successfully negotiated by the conjoint employment of the more conventional anti-foggant agents, i.e., to the exclusion of any necessity for the use of the more costly anti-foggant materials. The use of the polyoxyalkylenated pentaerythritol adducts described in the patent presents further advantages including for example, the reduction of brittleness and static in the film elements containing same. Despite the considerable advantage accruing with the use of the latter materials, it has nevertheless been observed that photographic elements containing same may not for all purposes possess optimum anti-static properties, i.e., to the extent that any requirement for the conjunctive use of specific anti-static compounds is necessarily obviated.

It was thus surprising as a concomitant to the discovery forming the basis of the present invention to ascertain that the employment of water-soluble polyoxyalkylenated pentaerythritol adducts of the type described in the aforereferenced patent, further derivatized, makes possible the obtention of the advantageous properties characterizing the non-ionic pentaerythritol-alkylene oxide adducts, e.g., improved speed, resistance to fogging, etc., while simultaneously imparting to photographic film elements containing same noteworthy improvement in anti-static properties.

Thus, a primary object of the present invention resides in the provision of improved light-sensitive silver halide emulsions as well as photographic elements fabricated therewith in which the aforedescribed disadvantages are eliminated or at least mitigated to a substantial extent.

A further object of the present invention resides in the provision of improved light-sensitive silver halide emulsions having exceptional anti-static properties and further characterized by outstanding photographic speed, contrast and covering power.

Another object of the present invention reside in the provision of improved light-sensitive silver halide emulsions having exceptional stability, e.g., resistance to fogging despite subjection to environmental conditions of high temperature and/ or humidity.

Other objects and advantage of the present invention will become apparent hereinafter as the description thereof proceeds.

The attainment of the foregoing and related objects is 4 made possible in accordance with the present invention which in its broader aspects provides bringing into operative association, i.e., contact with a light-sensitive photographic emulsion, a water-soluble acid ester of a pentaerythritol-alkylene oxide condensate of the following structural formula:

CH2-(O-R)aOH OH2(O-R)b0fl oHz(oR),oH

CI'I2(O'R)d-"OI'I wherein R represents an alkylene group having preferably from 2 to 4 carbon atoms, e.g., ethylene, propylene, isopropylene, butylene, etc. and the numerical values of a, b, c, and d are such that the molecular weight of the compound is within the range of from about 300 to 10,000 or more.

The polyoxyalkylenated pentaerythritol products may be prepared according to the process described in US. Pat. 1,970,570, the latter relating broadly to the preparation of condensation products of alkylene oxides with compounds containing a reactive hydrogen such as alcohols, phenols, amines, acids and the like.

The polyoxyalkylenated pentaerythritol acid esters of the present invention may be readily and conveniently prepared by introducing the acid esterifying agent in question, under elevated temperatures, e.g., 25 to 100 C., to a suitable vessel containing the polyoxyalkylenatedpentaerythritol material. The amount of acid added preferably ranges from about 0.2 mole to about 1.2 moles per mole of polyoxyalkylenated pentaerythritol. The acid addition will usually be effected over a period ranging from about 1 to about 4 hours. Upon completion of the acid addition, the reaction mixture is preferably heated to a temperature within a range of from to 125 C. and maintained at such temperature for a period ranging from about 2 to about 10 hours. Throughout the course of the reaction, the reaction vessel is purged with nitrogen in order to provide an inert atmosphere to the fullest extent possible.

In some cases depending upon the relative proportion of reactants, the reaction conditions, etc., the product obtained may comprise a composition of mixed esters, e.g., mono-, di-, tri-,, and tetra-, esters with varying amounts of non-ionic, i.e., non-esterified material. One of the salient advantages characterizing the present invention relates to the fact that such mixtures may be incorporated directly into photographic film elements absent further processing designed to effectuate separation of the various ester and/or non-ionic components.

In any event, should separation of ionic and nonionic be desired, such can be readily accomplished by the utilization of double bed ion exchange columns. Thus, the mixture of esters can be conveniently separated by merely passing same through a double bed ion exchange column; the ionic portion of the mixture remains in the column while the non-ionic portion passes therethrough and can be collected by suitable means provided for such purposes well known in the art. The recovered nonionic is of course available for re-use as a starting material in carrying out the esterification reaction. In general, it is found to be more convenient to employ the ester product for example, phosphate esters as a mixture i.e., mono-, di-, etc. ester derivatives and thereby obviate any necessity for restort to separative techniques by which to selectively isolate the respective ester components. In such cases, it has been ascertained that optimum results may be assured by regulating the relative proportions of esterifying agent and polyoxyalkylenated pentaerythritol so as to provide a reaction mixture containing significant proportions of the mono-ester. Thus, it has been determined that phosphate ester mixtures containing from to and higher of mono-ester can be produced by employing 115% polyphosphoric acid in lieu of phosphoric pentoxide as the phosphating agent. Complete esterification is assured in any event, i.e., to the exclusion of non-ionic material by the use of the theoretical or slightly higher mole ratios of agents, i.e, within the upper regions of the values hereinbefore stated. However, in order to assure optimum results, the proportion of the ester derivative should be such as to provide a mixture comprising at least 30% by weight and preferably at least 50% by weight of the ester based upon the entire product mixture.

The acid materials employed for forming the ester derivative of the polyoxyalkylenated pentaerythritol material may be selected from a wide variety of acids both organic and inorganic with typical representatives including without necessary limitation, sulfuric, phosphoric, sulfamic, sulfonic, acetic, propionic, and the like. However, the improvements provided by the present invention are found to obtain to a particularly effective extent when the acid employed comprises phosphoric, polyphosphoric, sulfuric, or sulfamic acid. Regardless of the particular acid selected for the esterification reaction, the preparation of the ester in question may be readily effected according to the aforedescribed procedure.

The sensitizer compounds contemplated for use in accordance with the present invention may be further represented by the following structural formula:

wherein a, b, c, and d have the aforedescribed significance and wherein R R R and R represent hydrogen or the anion of one of the aforedescribed acids with the provision that at least one of -R R R and R comprises said acid anion.

The improvements made possible by the present invention, i.e., increase in sensitivity, reduction of static, brittleness and the like, may be readily realized by incorporating the polyoxyalkylenated pentaerythritol acid ester in the light-sensitive silevr halide emulsion, undercoating, intermediate coating, overcoating, and/or surface coating, i.e., in such manner that the ester derivative is brought into intimate contact or association with the silver halide emulsion. The addition may be effected prior to the coating operation and, if desired, as an adjunct to the actual preparation of the emulsion either before or after washing. The proportions employed will depend to a great extent on the actual situs of such compounds, i.e., whether an integral component of the emulsion layer or an auxiliary layer and, of course, the type of emulsion employed. If added to a subbing layer, either one or two procedures may be employed; firstly, the ester material may be incorporated directly into the subbing layer composition prior to coating or alternatively, the applied sub may merely be treated with a 1 to solution of the ester in a water-misicble solvent, e.g., methanol, ethanol, propanol, isopropanol, etc. With silver halide emulsions of the high speed ammonia type it is found that the use of the ester material in concentrations ranging from 0.2 to about 10 grams per mole of silver halide is particularly beneficial. When incorporated into a non-sensitized auxiliary layer,'it is in general preferred that somewhat higher concentrations be employed, e.g., within the range of from about 1 to about 50 grams per mole of silver halide. It is in general advisable with embodiments of the latter type to utilize higher concentrations in order to insure that a sufficient amount of ester come into operative association with the sensitized emulsion layer, e.g., during development, and thereby realize the improvements contemplated herein. Without intending to be bound by any theory, it has been postulated in explanation of the synergistic improvement made possible by the present invention, that the polyoxyalkylenated pen'taerythritol ester materials characteristically diffuse or otherwise migrate to the sensitized emulsion layer and especially in the presence of solvent media such as the solutions employed in processing the exposed film, e.g., developer, fixer, etc. thus bringing about the desired intimacy of contact with the silver halide grains. For the vast majority of photographic applications, it will usually be found that concentrations within the range of from 0.3 to about 30 grams per mole of silver halide will be eminently satisfactory whether present in the sensitized emulsion layer or the auxiliary layer.

The polyoxyalkylenated pentaerythritol esters described herein may be advantageously employed in various types of photographic emulsions, e.g., in non-sensitized emulsions, orthochromatic, panchromatic, and X- ray emulsions. If used with sensitizing dyes, the ester material is preferably added either before or after dye addition. The light-sensitive emulsion may be prepared utilizing any of the conventional silver halide materials promulgated in the art for such purposes, e.g., silver bromide, silver iodide, silver chloride or mixed silver halides. Moreover, the emulsion employed may be adapted for use in either black and white photography or color photography. In the latter case, the emulsion will usually be provided with a developer compound of the primary aromatic amine type as well as a suitable color forming compound.

The dispersing agent or colloid carrier employed in the preparation of the layer composition, whether sensitized or non-sensitized, may be selected from any of those well known in the art for such purposes, e.g., hydrophilic film-forming materials such as gelatin, collodion, albumen, cellulose derivatives, synthetic polymeric substances such as polyvinyl alcohol, polyvinyl pyrrolidone, and the like. In general, the hydrophilic colloid employed must comprise a material whose aqueous solutions are capable of yielding a continuous film on drying.

The following examples are given for purposes of illustration only and are not to be regarded in any way as constituting a limitation on the present invention.

EXAMPLE I A silver halide emulsion in gelatin containing 4% silver iodide and 96% silver bromide is prepared in conventional manner and brought up to maximum light-sensitivity and coated onto a film base in a manner well known in the art. The film base thus coated is divided into two samples identified as (a) and (b). An aqueous gelatin solution containing 20 g. of gelatin per liter and 1.2 g. of the phosphoric acid ester of pentaerythritol is coated on the emlusion side of sample (a) as an antiabrasion layer. Sample (b) is coated in identical fashion with a similar gelatin coating composition but omitting the phosphoric acid ester. After drying, each of the film samples is exposed in a Type 1B Sensitometer and developed in a developer of the following composition:

Surface resistivityXlO- megohrns Sample 13% RH 72 F 22% RH 72 F 40% RH 72 F As clearly indicated by the above data, the polyoxyalkylenated pentaerythritol acid esters of the present invention make possible manifold reductions in surface resistivity of photographic elements containing same. Moreover such anti-static properties improve significantly with increased relative humidity.

The polyoxypropylenated pentaerythritol employed in the above example is prepared according to the following procedure.

Approximately 17.8 g. of P is added in incremental amounts over a period of approximately /2 hour to 200 g. of polyoxypropylenated pentaerythritol having a molecular weight of approximately 300 and 1.0 g. of hypophosphorous acid. The temperature is maintained within a range of from about to 40 C. throughout the P 0 addition. After all P 0 is added, nitrogen gas is bubbled through the reactants which are heated to 9095 C. and maintained at this temperature for approximately 4 hours under agitation. The mass is then cooled to approximately 80 C. whereupon 2.0 g. of a solution of hydrogen peroxide is added. The temperature is then maintained at 85 to 90 C. for a period of approximately 15 minutes. The product obtained was water white in appearance and is determined by analysis to comprise a mixture of monoester (31.2% by weight) and diester (23.2% by weight) with non-ionic constituting the remainder.

EXAMPLE II A silver halide emulsion in gelatin containing 4% silver iodide and 96% silver bromide is prepared in conventional manner and brought up to maximum light-sensitivity. The emulsion thus prepared is then readied for coating on a film base, that is, melted at C. and necessary coating finals added e.g., sensitizing dyes, stabilizers, and hardeners. Thereafter 10 cc. of a 10% aqueous solution of the phosphoric acid ester of polyoxypropylenated pentaerythritol having a molecular weight of approximately 600 is added to a sample of the aforedescribed emulsion the latter containing about 0.4 mole of silver halide. A sample of the same emulsion, but omitting the phosphoric acid ester derivative, served as a control. Each of the so prepared emulsion samples is coated on a cellulose ester base and dried. The emulsion samples are then exposed in a Type 18 Sensitometer and developed in a developer of the following composition:

Grams Metol 1.5 Sodium sulfite, anhydrous 45.0 Sodium bisulfite 1.0 Hydroquinone 3.0 Sodium carbonate, monohydrated 6.8 Potassium bromide 0.8

Water to make 1.0 liter.

The results obtained are tabulated as follows:

As the foregoing data makes manifestly clear, the significance inherent in the emulsion speed is realized in the virtual absence of any increase in fog. A determination of the anti-static properties of the respective film samples in the manner described in Example I yielded similar results, i.e., the acid ester compounds of the present invention made possible marked reductions in surface resistivity.

EXAMPLE III Example II is repeated except that 1 g. of polyoxyethylene laurylether having a molecular weight of approximately 350 is additionally included in the emulsion composition. Exposure and development is effected in a manner identical with that explained in Example II.

The results obtained are tabulated as follows:

EXAMPLES IV, V, VI

Examples 1, II and III are repeated except that in each case the phosphoric acid ester of polyoxypropylenated pentaerythritol is replaced with the same amount of the sulfuric acid ester of the polyoxypropylenated pentaerythritol having a molecular weight of approximately 450. Similar results are obtained, i.e., exceptional improvement in emulsion speed is realized while emulsion fog is reduced to an acceptable level. Moreover, the reduction in surface resistivity of the film element when compared to a control sample was similar to that described in Example I.

The polyoxypropylenated pentaerythritol sulfuric acid esters employed in Examples IV through VI is prepared in the following manner:

Approximately 240 g. of polyoxypropylenated pentaerythritol having a molecular weight of about 400 (0.6 mole) is charged to a 1 liter flask provided with an agitator and thermometer and heated to approximately C. under a nitrogen purge. Approximately 60 g. of sulfamic acid (0.62 mole) is added over a period of approximately 1% hours maintaining a solution temperature of from about 80 C. to about C. throughout the addition. Upon completion of the acid addition, the reaction mixture is heated to about to C. and maintained within this temperature for approximately 3 hours while continuing the nitrogen purge. Sufficient mono-methanolaminc, 15 g. is added so that a droplet of the solution exhibits an alkaline reaction on brilliant yellow paper. The reaction medium is thereafter cooled to approximately 90 C. and diluted with a mixture comprising 50 g. ethanol and g. water. The pH of the reaction mixture is then adjusted to a value of 6.7 by the addition of a 10% aqueous citric acid solution. The percentage of non-ionic material present in the esterified product can be confined to a value of approximately 5% or less by utilizing equimolar proportions of acid to polyoxyalkylenated pentaerythritol, or alternatively by employing the acid in excess. The percentage of nonionic can of course be increased by merely reducing the quantity of acid, e.g., sulfamic acid in which case produuct mixtures containing 50% non-ionic or higher can be obtained.

Results similar to those described in the foregoing examples are obtained when the procedures described therein are repeated but employing in lieu of the particular polyoxyalkylenated pentaerythritol acid ester exemplified, the sulfonic, citric, etc. acid esters of, for example, polyoxyethylenated pentaerythritol, polyoxy-l,2-butylenated pentaerythritol, and the like. i

As indicated hereinbefore, the molecular weight of the ester derivative may range from as low as 300 up to about 10,000 and even higher. In general, however, the lower molecular weight range would be preferred in those instances wherein the ester material is incorporated into an auxiliary layer, e.g., antiabrasion layer, undercoating, subbing, etc., in order to promote ease of diffusibility and thus assure maximum contacting of the sensitizing compound with the silver halide grains of the emulsion layer. Other factors may well influence the selection of a given molecular weight including, for example, its compatibility with the other ingredients of the composition, solubility, volatility, etc. The intermediate sub may be comprised of a single layer which may be either hydrophilic or hydrophobic in nature depending to a great extent on the type of base material employed. Alternatively, the sub may be comprised of a plurality of layers, e.g., separate layers of gelatin or other filmforming hydrophilic material and a resin layer substantially hydrophobic in nature, e.g., a vinyl acetatevinyl fluoride copolymer as well as analogous materials. In any event, compositions for such purposes are well known in the art being extensively described in the literature both patent and otherwise. As previously mentioned, incorporation of the ester material into one or more subbing layers can be eifected by including such ester as an ingredient of the subbing composition prior to coating or alternatively by merely treating the surface of the subbing layer following coating with a solution of the ester. With the latter embodiment, the ester material is confined for the most part to the surface portions of the subbing layer, penetration occurring by diffusion, inbitition, etc. Thus, the language present in a subbing layer is to be accorded the significance required by the foregoing explanation.

The present invention has been disclosed with respect to certain preferred embodiments thereof, and there will become obvious to persons skilled in the art various modifications, equivalents or variations thereof which are intended to be included within the spirit and scope of this invention.

What is claimed is:

1. A light-sensitive silver halide emulsion containing as a sensitizer and anti-static agent a compound comprising a water soluble acid ester of a polyoxyalkylenated pentaerythritol having a molecular wegiht of at least 300, the acid being a member selected from the group consisting of phosphoric, sulfuric, sulfamic, sulfonic, acetic, propionic and citric.

2. A light-sensitive silver halide emulsion according to claim 1, wherein said sensitizer and anti-static agent comprises the phosphoric acid ester of polyoxyalkylenated pentaerythritol.

3. A light-sensitive silver halide emulsion according to claim 1, wherein said sensitizer and anti-static agent comprises a sulfuric acid ester of polyoxyalkylenated pentaerythritol.

4. A light-sensitive silver halide emulsion according to claim 3, wherein said sensitizer comprises a water-soluble phosphoric acid ester of polyoxypropylenated pentaerythritol.

S. A light-sensitive silver halide emulsion according to claim 2, wherein said sensitizer and anti-static agent comprises a sulfuric acid ester of polyoxypropylenated pentaerythritol.

6. A light-sensitive photographic material comprising a base and containing at least one light-sensitive silver halide emulsion, said material containing as a sensitizer and anti-static agent a compound comprising a watersoluble acid ester of a polyoxyalkylenated pentaerythritol having a molecular weight of at least 300, the acid being a member selected from the group consisting of phosphoric, sulfuric, sulfamic, sulfonic, acetic, propionic and citric.

7. A light-sensitive photographic material according to claim 6, wherein said sensitizer agent is present in a lightsensitive silver halide emulsion layer.

8. A light-sensitive photographic material according to claim 6, wherein said sensitizer agent is present in an anti-abrasion layer.

9. A light-sensitive photographic material according to claim 6, wherein said sensitizer agent is present in a subbing layer.

References Cited UNITED STATES PATENTS 3,169,863 2/1965 Grabhafer et a1. 96l07 X 3,173,790 3/1965 Dersch et al. 96l07 3,385,708 5/1968 Grabhafer et al. 96l07 NORMAN G. TORCHIN, Primary Examiner R. E. FIGHTER, Assistant Examiner US. Cl. X.R. 9687 

